auto dimming rear view mirror - how do you know it works?

[KiwiME]

My 2014 Cross Polo has this feature but it doesn't seem to work that well. Following car's headlights are quite distracting. Anyone else who has this feature find it's working well, or not?

[RoknRob]

Just checking, but you know the feature can be turned on and off?
When mine is turned on (steady green light displayed) it works pretty well! I just have to turn it off when cars are behind me, and I can see the difference. It's a decent difference!

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[KiwiME]

Where do you turn it on/off? I haven't seen any green light and the owners manual does not mention this.
Thx for the response.

[staz88]

There's a button on the mirror.

[semblance]

Where do you turn it on/off? I haven't seen any green light and the owners manual does not mention this.
Thx for the response.

The green light tells you if its on or not. If you don't see a green light chances are it's not turned on. Button should be located just underneath the mirror

[wai]

You can tell it is working when the image turns a distinctly different shade.

[The_Hawk]

At the bottom in the middle of the mirror there is a single button. Turns on a green light to show the auto dimming is turned on. No light means the system is off.

One thing to note and an issue we hit in the Van is that it only works in the dark which is an automatic thing. The reason I mention this is because I went and mounted a dashcam behind the mirror (which hides it away nicely from the drivers view) but since the little screen stays active it puts enough light onto the light sensor in the mirror to make it think it's always daylight which in turn makes the dimming function never work.
We actually logged a fault with VW service because the auto dimming feature wasn't working and they quickly pointed out it was the dashcam causing the problem, moving it away from the sensor saw the mirror dimming away happily again as it should.

[KiwiME]

Thanks for all the responses. I've looked everywhere on that mirror and there is no button.
I can see the sensor behind the glass at the top-middle and the sensor in front at the left side, but nowhere is there any button.

My impression is that it is not working at all as there is no dimming when cars are following at night.

I'll try testing it with an LED light in the dark garage, while covering up the sunlight sensor. EDIT: Didn't work either but perhaps it needs the car to be moving.

[rufus001]

This is a silly question but what the heck. Are you absolutely certain your particular model has this feature? I was just wondering as you can't locate the button.

[RoknRob]

The button is pretty obvious on the bottom edge of the mirror. If it isn't there, your car probably doesn't have the feature.

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[brad]

post a photo. Sounds like it hasn't got it.

[DV52]

post a photo. Sounds like it hasn't got it.

brad: according to THIS, the 2014 Cross Polo 1.2 81kW DSG has an anti-dazzle mirror. So it should have a button that looks like this:

I know from experience that the anti-dazzle function won't work if the interior light is on- perhaps this is the problem (not sure)?

[wai]

The button is in the bottom near where the little green LED is. It is just about flush with the bottom of the mirror. You push it up from the bottom.

[KiwiME]

Thanks DV52 for actually looking that up! Yes, of course it has the feature, there certainly is no manual means to tilt the mirror and both sensors are present.

But it has neither the button nor the other feature just near it which I assume is the indicator light. The rear-facing sensor is at the top edge of the glass. Clearly it's a new design, the car is only a few months old. I can't find any setting anywhere in the Composition Media, or a button on the overhead console or the dash. Presumably it's fully automatic.

How close does a car need to be behind me to trigger it, and is it a gradual or sudden dimming?

Thanks for everyone who took the time to reply!

[DV52]

Thanks DV52 for actually looking that up! Yes, of course it has the feature, there certainly is no manual means to tilt the mirror and both sensors are present.

But it has neither the button nor the other feature just near it which I assume is the indicator light. The rear-facing sensor is at the top edge of the glass. Clearly it's a new design, the car is only a few months old. I can't find any setting anywhere in the Composition Media, or a button on the overhead console or the dash. Presumably it's fully automatic.

How close does a car need to be behind me to trigger it, and is it a gradual or sudden dimming?

Thanks for everyone who took the time to reply!

kiwiME: hi again - hope that you are enjoying your new car

The anti-dazzle mirror on the two VWs that I have operate by what's called "a differencing method". Whilst it could be entirely possible that your mirror is not the same, I would be extremely surprised if the method was different in your new model.

My understanding is that there are "smarts" in the mirror that compare the amount of light falling on the front sensor (the one near the windscreen, looking forward) and the amount of light falling on the rear sensor (the one pointing to the rear of the car). If the rear sensor is seeing a much higher level than the front sensor, the mirror starts to dim (the glass on the mirror has a type of liquid-crystal display - just like display on calculators where the numbers appear in black). The more the difference in light levels between the front and rear sensors, the more dimming occurs. During daylight the difference between front and rear light levels isn't high. But, at night, there is virtually no light falling on either of the two sensors, so a moderate amount of light on the rear sensor makes the mirror dim.

So, the distance of the car behind isn't really that important except that the further away the car behind is, the lower the light level will be on the rear sensor. The only thing that is important for the mirror to dim is the relative light levels on the two sensors.

An easy way the check the operation of the anti-dazzle mirror is to put your finger over the front sensor. This will mean that no light at all is seen by the front sensor and pretty-much any light that falls on the rear sensor will cause the mirror to dim. Shining a torch on the rear sensor with your finger on the front sensor makes a dramatic effect!

On both my cars, I have changed the operation of the dimming function by placing a piece of black electrical tape over the front sensor (very low-tech method). When I want the mirror to dim, I simply switch-on the button and I get maximum dimming.

The final point that I would make is that the anti-dazzle mirror won't dim at all if the interior lights are switched-on (as I said in my previous post). If your car is fitted with LED interior lighting, it's sometimes not obvious that these lights are switched on because of the other lighting in the cabin (and because of the fact that LED lighting is extremely directional).